The invention relates to a method and apparatus for making copies or duplicating from a suitable original such as a silver film or a diazofilm onto a diazo duplicate film, whereby ammonia gas is used for the developing.
It is known in the art to duplicate silver film onto a diazo duplicate film employing the principle of heliographic or so-called blueprint copying machines, whereby the duplicating film is exposed and thereafter developed in ammonia gas. The ammonia gas is produced by evaporating of ammonia water or ammonia crystals. This type of prior art method requires for its performance a substantial length of time.
It is further known to develope the diazofilm in the course of the prior art blueprinting under a high gas pressure, for example, six atmospheres gauge pressure. Due to the pressure application the development time is reduced so that one duplicate copy may be made per second.
The gas required for the performance of the prior art methods in producing the high pressure is obtained from commercially available gas bottles which are returned for a refill when their content is used up. Another disadvantage of the prior art development method is seen in that the amonia gas which has not been used up and which escapes when the developing chamber is opened must either be sucked-off or it must be collected in a container holding an absorber liquid. The installation of equipment for sucking off the ammonia gas not used up, is cumbersome. The frequent changing of the absorber liquid is expensive.